Well I have just recently updated to MyBB 1.6 and noticed that no one was registering so I tried registering a test account and I got this error:

MyBB has experienced an internal SQL error and cannot continue.

SQL Error:
1054 - Unknown column 'remember' in 'field list'
Query:
INSERT INTO mybb_users (`username`,`password`,`salt`,`loginkey`,`email`,`postnum`,`avatar`,`avatartype`,`usergroup`,`additionalgroups`,`displaygroup`,`usertitle`,`regdate`,`lastactive`,`lastvisit`,`website`,`icq`,`aim`,`yahoo`,`msn`,`birthday`,`signature`,`allownotices`,`hideemail`,`subscriptionmethod`,`receivepms`,`receivefrombuddy`,`pmnotice`,`pmnotify`,`showsigs`,`showavatars`,`showquickreply`,`showredirect`,`tpp`,`ppp`,`invisible`,`style`,`timezone`,`dstcorrection`,`threadmode`,`daysprune`,`dateformat`,`timeformat`,`regip`,`longregip`,`language`,`showcodebuttons`,`away`,`awaydate`,`returndate`,`awayreason`,`notepad`,`referrer`,`referrals`,`buddylist`,`ignorelist`,`pmfolders`,`warningpoints`,`moderateposts`,`moderationtime`,`suspendposting`,`suspensiontime`,`coppauser`,`classicpostbit`,`usernotes`,`remember`) VALUES ('test2','358119a38d86230055814ab9ede7a559','tYaHNob1','nNLLAdtQog8qpyvClAxQ6olWMEg7FdghhR2vsMI6EVCtg9ZNT9','[email protected]','0','./images/GF/avatars/The Games District Avatar.png','remote','5','','0','','1281270952','1281270952','1281270952','','0','','','','','test2, proud to be a member of The Games District since Aug 2010.','1','0','0','1','0','1','0','1','1','0','1','0','0','0','0','10','2','linear','0','','','81.98.227.86','1365435222','','1','0','0','0','','','1902','0','','','','0','0','0','0','0','0','0','','1')